Core barrel retrieval



United States Patent 72] Inventor Lyle J. Martinsen PrimaryExaminer-James A. Leppink Murray, Utah Attorney-Lynn G. Foster [21]Appl. No. 808,205 [22] Filed March 18, 1969 [45] patented 1 970ABSTRACT: Apparatus and method for retrieving a core bar- [73] AssigneeBoyles Bum Drilling Company rel assembly from its core-receivingposition at the leadlng end Salt Lake CiWUtah of a str1ng of drill pipe,the apparatus comprising an outer locking sleeve and an annular fittingdisposed partly within the locking sleeve and featuring an annular sealring interposed between the sleeve and fitting which (a) forms a fluidseal with [54] CORE BARREL RETRIEVAL the drill string when the annularfitting is advanced within the locking sleeve to foreshorten the overallapparatus and (b) 15 Claims, 4 Drawing Figs. I

breaks the fluid seal when the annular fitting 15 extended rela- [52]US. Cl 175/60; tive to the locking S]eeve An elongated Shaft aids inmaintairb 166/153, 166/156 ing the locking sleeve and annular fitting inthe foreshortened [51] Int. Cl EZlb 33/16; condmon within the drillString, to preserve the fluid Seal so E2 1 b 49/00 that the apparatus isdisplaced by the pressure of drilling fluid, [50] Field of Search175/60; mil h haft is axially dis laced counter to a bias upon im- 166/15 5 pact thereof with overshot latching structure of the core barrelassembly atthe leading end of the drill string adjacent the [56]References Cited outer tube whereupon the annular fitting is relativelyextended UNITED STATES PATENTS from the locking sleeve and the fluidseal is broken to accom- 2,589,656 3/1952 Armstrong 166/196 modatepassage of drilling fluid by the apparatus as the core 0 8/ 1962 Culvertal. 166/153 barrel assembly and apparatus, to which the core barrel as-3,052,302 9/1962 Lagucki u 6/1 sembly has latched are retrieved to thetrailing end of the drill 3,070,167 12/1962 Loy III et a1. 166/155string.

90 112 :30 I08 no s 2 62 |32\ 66 I24 56 5852 138 106 l "4] 4 6 I04 us I?as 95 1. il no 7 Q 122/100 176 I02 I66 1 CORE BARREL RETRIEVAL FIELD orrue INVENTION The present invention relates to retrieval of a corebarrel assembly from the remote end of a string of drill pipe (drillstring) and, more particularly, to novel method and apparatusaccommodating hydraulic pressure displacement of the retrieval unit tothe core barrel assembly, coupling of a novel retrieval unit to the corebarrel assembly and subsequent retrieval of both the retrieval unit andcoupled core barrel assembly without, at the same time, swabbing thehydraulic drilling fluid from the drill hole. The invention furtherrelates to producing a hydraulic or fluid seal between the drill stringand the retrieval unit during pressure displacement thereof to the drillsite and automatically removing the hydraulic seal upon impact with thecore barrel assembly and during said retrieval.

As used herein, drill string" means consecutive lengths of joined drillpipe, comprising a terminal outer tube, disposed in a hole and corebarrel assembly means the combination of the core-receiving inner tube,the swivel mechanism and the outer tube-coupling latch structure andexcludes the outer tube to which the latch structure is coupled duringdrilling.

BACKGROUND OF THE INVENTION It has been a longstanding problem in thecore drilling art to efficiently displace a retrieval unit, particularlyin a horizontal or in an up" hole to its coupling position with a corebarrel assembly disposed adjacent an outer tube at the leading end ofthe drill string. Proposed prior art devices, to my knowledge, generallyconsist of a plurality of parts, which cooperate and which cause ahydraulic seal to be formed with the drill string to allow the corebarrel assembly to'be displaced axially by hydraulic pressure.Conventional structure, attached to a wire line is required in order toretrieve the core barrel assembly from its drilling position. This wireline (cable) attachment dramatically curtails the rate at which theretrieval structure can be hydraulic-pressure-displaced within the drillstring because the resistance to displacement comprises (a) the frictioncreated by the seal of the retrieval structure, (b) the load or weightof the wire line, (c) the resistance of the packing gland seal at thepump end of the drill string which squeezes the wire line and (d) thelow speed limitation imposed in order to avoid tangling with the wireline. More specifically with regard to (d), after the retrievalstructure has coupled to the core barrel assembly for removal from anoverhead hole, the drill string must be intentionally drained, at acontrolled rate in order to maintain a fluid back pressure to controldescent and thereby prevent wire line tangle. This retrieval processrequires a substantial and expensive amount of time.

Later, the same prior art retrieval structure is used to again place thecore barrel assembly in its drilling position, and, thereafter, when theretrieval structure is returned to the trailing end of the drill stringthe hole is once more swabbed dry, requiring additional time tosubsequently refill the drill string with drilling fluid prior toresumption of drilling.

When drilling in a near horizontal down hole, the seal of commercialretrieval structures, undesirably will swab the hole dry of drillingfluid during retraction of the retrieval structure and core barrelassembly. Attempts to avoid swabbing the hole dry have recently beenmade for drilling in a down hole. For example, see US. Pat. No.3,333,647. Nevertheless, the requirement that such devices use a wireline to operate properly, continues to inflict the problems abovementioned.

BRIEF SUMMARY AND OBJECTS OF THE PRESENT INVENTION It is a primaryobject of the present invention to overcome or alleviate problems of thementioned type.

The mentioned primary object is accomplished by the present invention,which includes method and apparatus. The apparatus comprises a pump-inretrieval unit having structure for creating a hydraulic seal betweenthe drill string and the pump-in unit for hydraulic displacement withinthe drill string prior to coupling of the retrieval unit with the corebarrel assembly. The hydraulic seal is removed upon coupling with thecore barrel assembly.

The pump-in or retrieval unit generally comprises telescopicallyinterrelated members which are relatively axially displaceable betweenopen and closed positions. Expandable seal structure is situated betweenthe two members and rests upon bridging structure, so that when the unitis in the closed position, the seal structure will be expanded by thebridging structure outwardly beyond the periphery of the unit to form afluidtight seal between the retrieval unit and the drill string.

When the members of the unit are in the open position, the sealstructure is allowed by the bridging structure to contract away from thedrill string thereby breaking the fluidtight seal.

The telescopically-interrelated members of the unit are displaced fromthe closed or retracted position to the open or extended position whenthe unit, being displaced within the drill string under pressure,strikes the latch structure of the core barrel assembly so that lockingstructure holding the members in the closed position is released toaccommodate relative displacement of the two members away from eachother.

Therefore, it is another primary object of the present invention toprovide novel method and unique apparatus for displacement of a corebarrel assembly retrieval structure to the leading end of a drill stringby force of drilling fluid.

One still further significant object is to provide improved structurefor selectively forming and breaking a seal with a pipe in which thestructure is disposed.

Another paramount object is the provision of novel structure and methodfor retrieving a core barrel assembly such that a fluid seal ismaintained between the apparatus and a drill string to accommodatedisplacement of the apparatus by pressure, the fluid seal being brokensolely by impact between the apparatus and the core barrel assembly atthe drilling site.

One still further important object of the present invention is toprovide novel structure which maintains one member of a retrieval unitin a closed or retracted position relative to anothertelescopically-related member to maintain a fluid seal until the corebarrel assembly is struck by the retrieval unit whereupon the membersare unlocked accommodating limited relative movement therebetween intoan open position.

It is another significant object of the present invention to provide aunique core barrel assembly retrieving apparatus and method which isparticularly effective in up" and in generally horizontal holes, andwhich may be used without a wire line.

These and other objects and features of the present invention willbecome more fully apparent from the following description and appendedclaims taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevation shown partially in cross section illustratinga presently preferred embodiment of a retrieval unit, constructed inaccordance with the present invention and disposed in its locked, sealedcondition;

FIGS. 2 and 3 are side elevations shown partially in cross sectionsimilar to FIG. 1 illustrating the retrieval unit of FIG. 1 (a) in theinstantaneous position it assumed immediately upon impact with the corebarrel assembly (FIG. 2) and (b) in the position it assumes immediatelyafter the position of FIG. 2 is achieved (FIG. 3); and

FIG. 4 is a cross-sectional illustration of a wire line adapter whichmay be used with the embodiment of FIGS. 13.

THE DETAILED DESCRIPTION OF THE ILLUSTRATED RETRIEVAL UNIT Withreference to the FIGS., it should be observed that like numbers identifylike parts throughout. With reference particularly to FIG. 1, theretrieval unit, generally designated 30, is illustrated in the closedand locked fluid sealed condition with the drill string 20. Theretrieval unit 30 forwardly presents a shoe 32 having a hollowinterior36, the shoe being adapted to couple with a core barrel assembly(not shown).

For coupling purposes, the interior 36 of the shoe 32 is provided with abell-shaped recess 40 the trailingportion 38 of which is inwardlytapered to define a shoulder and the leading portion of which isprovided with an annular core barrellatching shoulder 42 which extendsthrough 360 of the interior surface of the shoe 32. Shoe 32 opens at theleading end 44 so that the spearhead latching structure 190 of a corebarrel assembly may enter therethrough as shown in FIG. 2.

The spearhead latching structure 190 (FIG. 2) comprises prongs orresilient fingers 192 which are attached to the remainder of the corebarrel assembly (not shown). The prongs 192 are outwardly biased, eachhaving identical construction and comprising a coupling ridge 194 havingoutwardly diverging abutment surfaces 196 and 198 and an exteriorarcuate mating surface 200 which couples directlywith the outer tube ofthe drill string 20.

Each prong 192 further comprises a spearhead hook 204 having an exteriortapered though arcuate surface 208 and an overshot latching shoulder 206adapted toabut shoulder 42. The shoulder 206 is separated from theadjacent coupling ridge 194 by an arcuate groove 202 disposed in eachprong.

The trailing end of shoe 32 is provided with a threaded aperture 34which engages a threaded boss 52 comprising the leading end of anexterior housing or locking sleeve generally designated 50.

Locking sleeve 50 exteriorly presents a smooth cylindrical surface 70which is chamfered at 56. The forward abutment face 58 adjacent thechamfer 56 provides a smooth surface against which the trailing end ofthe shoe 32 is contiguously disposed.

The locking sleeve 50 is centrally hollow and provided with a smoothinterior surface 62, the hollow interior having a leading interiorabutment surface60. A central aperture 55 exists through the center ofthreaded boss 52 of the locking sleeve 50 and opens to the interior ofthe locking sleeve 50 at the abutment surface 60. Also, one or morebleeder ports 54, which are essentially parallel to the aperture 55, aredisposed in the boss 52 slightly spaced from aperture 55. Each bleederport 54 accommodates passage of drilling fluid through the lockingsleeve 50. Aperture S displaceably receives a central shaft generallydesignated 150, which will be subsequently more fully described. 7

The internal surface 62 0f the locking sleeve 50 is inter ruptedadjacent the'trailing end 68 thereof with an annular groove 64. Anannularly, outwardly tapered surface 66 is disposed between the groove64 and the trailing end68 of the locking sleeve 50.

One or more stepped bores 72 are disposed intermediate the length of thelocking sleeve 50, the reduced diameter portion of each bore 72 beingthreaded to threadedly receive set screw 74 at reduced shank portion 76.Shank 76 projects into the interior of the locking sleeve 50 beyond thesmooth surface 62. The purpose and function of each setscrew 74 will behereafter set forth.

Telescopically disposed within the interior 62 of the locking sleeve 50is an inner annular fitting or core, generally designated 90, the core90 having an annular leading end 92 disposed within and spaced slightlyfrom the interior surface 62 and which presents a forward abutment face94 which cooperates with abutment face 60 to confine a compressionspring 95. Spring 95 continuously biases the annular core 90 axiallyaway from the locking sleeve 50. The leading end 92 of the annular coreis provided with (a) a central aperture 96 through which a portion ofthe central shaft 150 is reciprocably disposed and (b) a bleeder port 98which provides for passage of drilling fluid. Aperture 96 and bleederport 98 open at the trailing face 100 into a diametrically enlargedgenerally cylindrical chamber 102, which chamber terminates at thetrailing surface 104.

The annular core terminates in an enlarged cylindrical portion which hasa forward-directed annular shoulder 112 at the leading end and atrailing abutment surface 108. The cylindrical portion 110 is interiorlythreaded at 106 between the trailing end 108 and the surface 104. Thecylindrical member 110 has an outside diametral dimension which issubstantially the same as the diametral dimension of the exteriorhousing or locking sleeve 50.

The exterior of the inner core 90, most of which is normally disposedtelescopically within the locking sleeve 50, is provided with adiametrically tapered ramp 114 between the shoulder I12 and theessentially cylindrical surface portion 116. A plurality of transverseapertures 117 are disposed within the cylindrical portion 116 of theannular core 90. As illustrated in FIG. 1, each aperture 117 is adaptedto be placed in substantial alinement with the annular groove or recess64 of locking sleeve 50 when, the annular core 90 is retracted withinthe locking sIeeveJA spherical ball 65, preferably of surface-hardenedmetal, is loosely disposed within each aperture 117. Itis preferred thateach ball 65 be slightly smaller in diameter than the associatedaperture 117 and have a diametral dimension which is greater than theaxial dimension of the aperture 117 (i.e., the thickness of the core 90at each aperture 117) so that, in the closed or retracted positionillustrated in FIG. 1, each ball 65 will project into the groove 64 toprevent axial displacement of the inner core 90 relative to the exteriorlocking sleeve 50.

Cylindrical portion 116 of the core 90 is also provided with an axiallyelongated exteriorly-open slot 120 for each setscrew 74, which receivesthe exposed shank 76 of the setscrew. Each slot 120 terminates in aforward end 124 and a trailing end 122, the ends 124 and 122 beingadapted to abut the shank 76 of setscrew 74 to define the limit to whichthe annular core 90 may be axially displaced within and relative to thelocking sleeve 50.

A resilient, expandable annular ring, such as an O-ring 118, iscontiguously carried upon the tapered ramp surface 114 between theshoulder 112 and the abutment face 68 of the locking sleeve 50. When theannular core 90 and the locking sleeve 50 are in the retracted or closedposition illustrated in FIG. 1, the inside and outside diameters of theannular ring 118 are forced to the diametrically enlarged left end ofthe ramp surface 114 so that the annular ring 118 is expanded radiallyoutward tightly against the interior surface 22 of a drill string 20.Thus, a fluid seal is formed between the drill string 20 and retrievalunit 30 when the annular core 90 and the exterior housing or lockingsleeve 50 are in the closed position of FIG. I.

An insert or cap, generally designated 130, in FIGS. 1-3, comprises abody 132 having, at the trailing end thereof, a smooth rear face 134and, at transverse face 136 thereof, a forwardly projecting, exteriorlythreaded annular boss 138 which is screw-secured into the cylindricalportion 110 of the annular core 90 at 106 until faces 108 and 136 meet.The boss 138 is provided with a planar abutment surface 140 whichcommunicates with and is illustrated as being spaced slightly from theface 104 of the inner core 90. The abutment face 140 abuts one end of acompression spring 176 which biases the central shaft 150 toward itsmost projected rightward position, illustrated in FIG. 1.

If desired, the cap may be replaced by cap 250, shown in FIG. 4. Cap 250resembles cap 130 in that it comprises the boss 138, abutment surfaceand face 136 and is attached to the annular core 90 in a substantiallyidentical manner. The

' body 252 of the cap 250 is substantially longer than body 132 of cap130 and body 252 is provided with an axial blind bore 254 having threads256. The bore 254 opens into an annular recess 258, the recess 258-andthreads 256 being adapted to receive a conventional wire line attachment(not shown). The embodiment of FIG. 4 is used with a wire line, forexample, in horizontal or down holes where the force of gravity will notbring the retrieval unit to the trailing end of the drill string.However, it may also be used without a wire line.

The central shaft 150 comprises a smooth exterior portion 152 having athreaded leading end 154 which terminates in a substantially flat end162. A retainer nut 156 and an impact nut 158 are threadedly attached tothe end 154 of shaft 150, the impact nut 158 comprising an impactsurface 160 which faces the opening 44 in the shoe 32.

The central shaft 150 is disposed through both aperture 55 in theexterior housing 50 and aperture 96 in the inner core 90. The shaft 150terminates at the trailing left end thereof in a stepped annularenlargement having a lower step 164 with a forwardly directed abutmentface 166 and rearwardly merging with the annularly enlarged upper step170 over an annular ramp surface 168. The annularly enlarged step 170terminates rearwardly in a tapered edge 172 and a planar face 174 uponwhich the compression spring 176 bears to urge the central shaft 150 inthe projected position illustrated in FIG. 1.

OPERATION OF THE RETRIEVAL UNIT When it is desired to use the retrievalunit in a horizontal or up hole and to propel the retrieval unit to acore barrel assembly at the leading end of the drill hole by thehydraulic pressure of drilling fluid, the retrieval unit 30 is placed inthe contracted position by forcing the inner core 90 telescopicallywithinthe locking sleeve 50 against the bias of compression spring 95until each aperture 117 is alined with the annular groove 64. Thiscauses the central shaft 150 to be drawn to the projected positionillustrated in FIG. 1 so that the spherical ball 65 within each aperture117 will ride up the ramp 168 and rest upon the annularly enlargedportion 170 of the shaft 150. In this position, a portion of each ball65 is within the associated annular groove 64 and another portion iswithin the associated aperture 117 to releaseably lock the inner core 90and the locking sleeve 50 in the position illustrated in FIG. 1.

The retracted or closed position of the inner core 90 relative to thelocking sleeve 50 forces the resilient annular ring 118 to thediametrically enlarged portion of ramp 114 at the left so that the ring118 radially expands and forms a fluidtight seal with the smoothinterior surface 22 of the drill string 20. In this position, hydraulicfluid acting primarily upon the surface 134 of the cap 130 (see thearrows of FIG. 2) will propel the retrieval unit 30 through the drillstring to the location of the core barrel assembly at the drilling site.

As illustrated in FIG. 2, when the overshot bell receives the spearheadhook 204 of the prongs 192, the prongs 192 are gathered together withinthe shoe 32 until the leading end 210 of each prong 192 strikestheimpact surface 160 of nut 158. instantaneously the impact force iscommunicated from the prongs 192 through the impact locknut 158 to thecentral shaft 150 and displaces the central shaft 150 axially rearward(left) against the bias of compression spring 176 until each sphericalball follows the ramp 68 to the reduced stepped portion 164 of the shaft150. In the FIG. 2 position, which is the instantaneous position atimpact, the spherical balls 65 are forced radially inward throughapertures 117 toward shaft 150. The compression spring 95 theninstantaneously axially displaces the inner core 90 re'arwardly (left)relative to the exterior housing 50 to the extended position illustratedin FIG. 3. Engagement of the balls 65 with interior surface 62 of thehousing 50 and with the ramp surface 168 of the shaft 150 restrains theshaft in the position'of FIG. 3 counter to the bias of spring 176. Theamount of displacement of the inner core 90 relative to the exteriorhousing or locking'sleeve 50 is limited by engagement of the abutmentshoulders 122 and 124 by the shank 76 of each setscrew 74.

In the extended position, illustrated in FIG. 3, the radially expandableresilient ring 118, which is made of wear resistant material withmemory, will have moved along the ramp surface 114 to the diametrallyreduced cylindrical portion 116 of the annular core 90 due to the memoryof the material. As the expandable ring 118 moves to the reduceddiametral portion, the inside and outside diameters of the ring 118'concurrently contract due to said resilience or memory to move the ring118 out of sealed relation with the surface 22 of the drill string 20thereby breaking the fluid seal between the retrieval unit 30 and thedrill string 20.

When the retrieval unit 30 is axially displaced through the outer tube20 toward the trailing end of the drill string, the lower couplingshoulder 206 of the prongs 192 will engage the annular core barrellatching shoulder 42 so that the core barrel assembly is withdrawn alongthe the retrieval unit. In an up" hole, the return of the retrieval unit30 and core barrel assembly is preferably accommodated without a wireline by force of gravity with the drill pipe being drained as rapidly aspossible until only enough drilling fluid remains to adequately cushionthe fall of the retrieval unit at the trailing end of the drill string.

However, in a down" hole, the return must be effectuated by a wire lineattached to the cap embodiment 250 (FIG. 4), secured as described to theretrieval unit 30. In either case, the present invention forms a sealwith the drill string prior to latching with the core barrel assemblywhich seal is automatically broken when the core barrel assembly isimpacted by the novel retrieval unit 30.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is, therefore, to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore to be embraced therein.

Iclaim:

1. Apparatus for fluid pressure displacement through a string of drillpipe terminating in an outer tube to latch with and retrieve a corebarrel assembly disposed within and coupled to the outer tube duringdrilling comprising:

an exterior housing having a maximum transverse dimension less than theinside transverse dimension of the outer tube and the drill pipe;

resilient seal means adjacent the exterior housing which,

when in one position, are radially expanded to a transverse sizeslightly greater than the inside transverse dimension of the outer tubeand the drill pipe to create a seal between the drill pipe or the outertube and the apparatus adjacent the periphery of the housing to preventdrilling fluid from passing between the apparatus and the drill pipe orouter tube;

axially displaceable substantially water-impenetrable meanstelescopically carried at least partially within the housing andrelatively displaceable from an extended disposition to afluid-obstructing retracted disposition for expanding the seal meansinto the one position and thereafter maintaining the seal means in theone position so long as the axially displaceable means are in theretracted disposition; and

means partially telescopically disposed within both the housing and theaxially displaceable means and responsive to the impact of the apparatusagainst the core barrel assembly, the responsive means comprisinglocking means releasably coupling the housing and the displaceable meanswhen in the fluid-obstructing retracted disposition and meanstransferring the impact force to the locking means to release thelocking means and effect relative axial displacement of the displaceablemeans from the retracted disposition to the extended dispositionaccommodating transverse contraction of the seal means due to theresilience thereof to terminate said seal and allow for fluid flowbetween the apparatus and the drill pipe or the outer tube.

2. Apparatus of the type defined-in claim 1 wherein said seal meanscomprise an annular ring composed of a material with memory.

3. Apparatus of the type defined in claim 1 wherein one end of thehousing abuts the seal means and the axially displaceable means comprisea diametrically tapered ramp fitted through a hollow center of the sealmeans so that movement of the displaceable means from the extended tothe retracted disposition drives the seal means up the ramp by reason ofthe abutment with the housing thereby radially expanding the inside andoutside transverse dimensions of the hollow seal means to create saidseal.

. 4. Apparatus of the type defined in claim 1 wherein the responsivemeans comprise a central shaft partially telescopically disposed withinthe axially displaceable means, the shaft being adapted to be contactedby the core barrel assembly upon impact and thereby axially displacedaccommodating release of the locking means to provide for relativemovement of the displaceable means and the housing into the extendeddisposition.

5. Apparatus of the type defined in claim 4 wherein the locking meansare interposed between the housing and the central shaft and are urgedagainst the housing by an enlarged portion of the shaft when the axiallydisplaceable means are in the retracted disposition, the locking meansmoving away from the housing when the enlarged portion is displaced awayfrom the locking means upon impact of the apparatus against the corebarrel assembly.

6. Apparatus of the type defined in claim 1 further comprising meansinterposed between the axially displaceable means and the responsivemeans urging the axially displaceable means and the responsive meansaway from each other.

7. Apparatus of the type defined in claim 1 further comprising meansinterposed between the housing and the axially displaceable meansbiasing the axially displaceable means toward the extended disposition.

8. Apparatus of the type defined in claim 1 further comprising stopmeans interposed between the housing and the axially displaceable meanslimiting the permissible relative movement therebetween and therebydefining the extended and retracted dispositions.

9. Apparatus of the type defined in claim 1 further comprising couplingmeans integral and coaxial with the exterior housing at the leading endthereof for latching the apparatus to the core barrel assembly uponimpact.

10. A pump-in unit for fluid pressure displacement through a string ofdrill pipe to an outer tube comprising the terminal section of thestring to latch with and retrieve a core barrel assembly disposedadjacent and coupled to the outer tube comprising:

a central axially directed shaft having an annularly enlarged portionnear the trailing 'endof the shaft;

a locking sleeve concentrically circumscribing the enlarged portion ofthe central shaft having an internal annular locking groove;

a generally annular core disposed between the central shaft and thelocking. sleeve, the core having a plurality of transverse aperturesopening to both the central shaft and the locking sleeve and an externalramp surface at least part of which is disposed rearward beyond thetrailing end of the sleeve and defining a gradually rearwardlyincreasing radial dimension;

spherical balls loosely disposed one in each of the apertures in thecore, each ball having a diameter somewhat greater than the end-to-endlength of the aperture so as to be projectable into the annular groovein the locking sleeve when the central shaft is so disposed that theenlarged portion is in locking position contiguous with the balls and tobe removed frorn'the annular recess toward the shaft when the enlargedportion is displaced away from the balls; and diametrally expandableO-ring carried upon-the exterior ramp surface of the core which isexpandable into fluidsealing relation with the drill-pipe or outer tubeby relative displacement of the O-ring with respect to the ramp surfacein a rearward direction until the balls are continuous with the annulargroove in the locking sleeve and is contracted out of fluid-sealingrelation with the drill pipe or outer tube by relative displacement ofthe O-ring with 11. A pump-in unit of the type defined in claim 10wherein said core is normally biased in an axial direction away from thelocking sleeve so that the core will move relative to the locking sleeveautomatically when the spherical balls are away from the annular groove.

12. In a method of coupling and retrieving a core barrel assemblydisposed at the leading end of the string of drill pipe using aretrieving unit:

positioning an inner core of the retrieving unit having an exterior rampsurface relative to an exterior housing of the retrieving unit so thatan expandable seal resting upon the ramp surface is expanded by relativedisplacement of the ramp surface with respect to the seal to form afluid seal with the string; restraining the seal in the expandedfluid-seal position; displacing the retrieving unit under pressure ofdrilling fluid through the string causing the unit to strike and couplewith the core barrel assembly free of the string; and

changing the relative positions of the inner core and the exteriorhousing upon striking the core barrel assembly to relatively displacethe ramp surface with respect to the seal so as to cause the expandableseal to contract thereby terminating the fluid seal.

13. In a method of the type defined in claim 12 further comprisingreturning the retrieving unit and the coupled core barrel assembly tothe trailing terminal end of the string while simultaneously allowingrelative flow of the drilling fluid between the string and theretrieving unit.

14. Apparatus for retrieving a core barrel assembly from its drillingposition at the leading end of a drill string:

a resilient annular seal;

a water-impenetrable diametrically tapered section passing through andcontiguous with the hollow of the annular seal;

means restraining the annular seal to accommodate enlargement of theinside and outside diameters of the sea] by relative displacement of thetapered section with respect to the annular seal from an open to aclosed position, the outside diameter of the annular seal in the closedposition being slightly greater than the inside diameter of the drillstring to create a fluidtight relation therebetween when the apparatusis in the drill string;

means (a) for reversibly coupling the tapered section and restrainingmeans to maintain the annular seal in the closed position while theapparatus is displaced under pressure of drilling fluid until theapparatus reaches the core barrel assembly and (b) for incoupling thetapered section and the restraining means to return the annular seal tothe open position with the inside and outside diameters of the annularseal being contracted due to the resilience of the seal followingcontact with the core barrel assembly to terminate the fluidtightrelation; and

means for coupling the apparatus to the core barrel assembly forretrieving the core barrel assembly.

15. Apparatus for transversely sealing the interior of a pipe againstfluid flow across the apparatus:

first and second telescopically-interrelated members which areselectively displaceable with a tapered section disposed therebetween,said members each having a maximum transverse dimension less than theinside diameter of the pipe and together obstructing fluid passageexcept between the exterior periphery of the members and the interiorperiphery of the pipe;

structure for relatively positioning and reversibly restraining themembers in an open extended position or a closed retracted position; and

an endless annular seal made of a material having memory mounted betweenportions of said first and second members upon the tapered section at acentral opening in the seal which opening is sized to cause the seal toconcausing the inside and outside diameters of the endless seal to beenlarged when the members are relatively displaced toward each otheruntil the closed position is obtained where the outside diameter of theseal is greater than the inside diameter of the pipe.

